Evaluating the Effects of the Nonplanarity of Nucleic Acid Bases on NMR, IR, and Vibrational Circular Dichroism Spectra: A Density Functional Theory Computational Study

The benchmark of 31P NMR parameters in phosphate: a case study on structurally constrained and flexible phosphate

A benchmark for structural interpretation of the ³¹P NMR shift and the ²J_P,C spin–spin coupling in the phosphate group was obtained by means of theoretical calculations and measurements in diethylphosphate and 5,5-dimethyl-2-hydroxy-1,3,2-dioxaphosphinane 2-oxide.

Guanine bases in DNA G-quadruplex adopt nonplanar geometries owing to solvation and base pairing

The effect of base pairing and solvation on pyramidalization of the glycosidic nitrogen found in the residues of parallel G-quadruplex with NDB ID UDF062 is analyzed and explained with theoretical calculations. The extent of the pyramidalization depends on the local geometry of the 2'-deoxyguanosine residues, namely on their glycosidic torsion and sugar pucker, which are predetermined by the 3D-architecture of G-quadruplex. Pyramidal inversion of the glycosidic nitrogen found in 2'-deoxyguanosines of G-quadruplex is induced owing to site-specifically coordinated solvent. Different adiabatic structural constraints used for fixing the base-to-sugar orientation of 2'-deoxyguanosine in geometry optimizations result in different extents of pyramidalization and induce pyramidal inversion of the glycosidic nitrogen. These model geometry constraints helped us analyze the effect of real constraints represented by explicit molecular environment of selected residues of the G-quadruplex. The maximal extent of the glycosidic nitrogen pyramidalization found in the high-resolution crystal structure corresponds to the calculation to deformation energy of only 1 kcal mol(-1). The out-of-plane deformations of nucleobases thus provide a way for compensating the site-specific external environmental stress on the G-quadruplex.